Though there are many different keyword research tools out there, the three most respected are: WordTracker, Keyword Discovery and Overture.

While I’m least familiar with WordTracker, I can say that my minimal experience as an SEO copywriter and some research seems to indicate that there is no magical, one-stop shop keyword research tool that’s precise enough to give you everything you want or need. All of the big three have their advantages, with Overture being the most limited.

When researching keywords, a range of sources – from SEO for dummies to Karon Thackston at MarketingWords.com – suggest that solely relying on results from keywords is not a smart way to accurately conduct keyword research. Using some marketing savvy combined with additional research is more likely to produce the results you want.
Jill Whalen, a trusted authority on SEO copywriting, recommends WordTracker in her book “The Nitty-gritty of Writing for Search Engines.” In the SEO for Dummies book, author Peter Kent goes through a mini-tutorial on this tool, and I’ve read several articles that discuss the merit of WordTracker. Just like the other tools, the results represent a sampling of results across several databases all over the Web.

Keyword Discovery seems to work in much the same way, and offers anaysis tools similar to WordTracker. And I’ve ready positive reviews of KD as well, and Jill Whalen says she uses this tool in addition to WordTracker. The difference between the two (it seems), is that Wordtracker was created first, so it has more merit than Keyword Discovery because it is older. And depending on what type of information you’re looking for, one may be better than the other, but from what I’ve read that determination seems pretty subjective, more based on preference than on fact because both tools are pretty comparable.

Overture is a good, quick & easy keyword research tool that doesn’t really offer extensive analysis, and tells you how often a search term has been searched on over the last month.

So, there does not really seem to be a “best” keyword research tool. Keyword research remains more of a trial and error marketing research process than just a task that can be accomplished with a couple of clicks of the mouse. And in his article, “Keyword Data is Almost Always Wrong,” author Jay Stockwell offers an interesting perspective when comparing keyword results – for the same term – between the big three and a couple of other research tools.